Automotive rotary electric machine

ABSTRACT

The present invention provides an automotive rotary electric machine enabling brush abrasion limit detection reliability to be increased and stable brush abrasion limit detection indication to be performed. The construction thereof is provided with a detecting terminal for sensing a brush abrasion limit when a brush has abraded to a predetermined length by coming into contact with a coil spring that forces the brush, and a determining circuit constructed so as to compare output from the detecting terminal and a threshold value, to enter an ON state (a brush abrasion limit detection state) once the output exceeds the threshold value, and thereafter to maintain the ON state. Thus, because the ON state of the determining circuit is maintained even if output from the detecting terminal fluctuates due to vibration, noise, etc., false detection of the brush abrasion limit resulting from the fluctuations in the output from the detecting terminal can be prevented.

TECHNICAL FIELD

The present invention relates to a rotary electric machine mounted to anautomotive vehicle such as a passenger car, a truck, an electric train,etc., and particularly to a control apparatus for detecting an abrasionlimit of a brush mounted to a rotary electric machine.

BACKGROUND ART

FIG. 11 is a circuit diagram explaining an electrical circuit for anautomotive vehicle mounted with a conventional automotive alternatorsuch as that described in Japanese Patent Laid-Open No. SHO 57-101549(Gazette), for example, and FIG. 12 is a cross section showing aconstruction of a power supply mechanism portion in the conventionalautomotive alternator.

In conventional automotive alternators, when a key switch 105 is closed,an electric current flows from a storage battery 104 through the keyswitch 105, a positive electrode brush 109, a field winding (a rotorwinding) 102, and a negative electrode brush 110 to a power generationcontrol apparatus 108. The field winding 102 is excited with a directcurrent by this electric current.

In this state, when a rotor is driven to rotate by rotation of anengine, a rotating magnetic field is applied to an armature winding (astator winding) 101, giving rise to an electromotive force in thearmature winding 101. This alternating-current electromotive force isconverted into a direct current by a three-phase full-wave rectifier103, and serves to charge the storage battery 104. Thisalternating-current electromotive force is also converted into a directcurrent by an auxiliary rectifier 107 and is supplied to the fieldwinding 102. As the rotational speed of the rotor rises, the powergeneration control apparatus 108 controls the electric current flowingthrough the field winding 102 such that the voltage of the storagebattery 104 is constant.

Now, the positive electrode brush 109, as shown in FIG. 12, is housedinside a brush holder 125 so as to be pushed outside by a force from acoil spring 126. Moreover, although not shown, the negative electrodebrush 110 is also similarly housed inside the brush holder 125. Thus,the positive electrode brush 109 and the negative electrode brush 110,due to the force from the coil springs 126, slide in contact with sliprings (not shown) functioning as current receiving portions rotatingtogether with the rotation of the rotor, tip portions thereof beinggradually abraded. The electric current flows through the positiveelectrode brush 109, a slip ring, the field winding 102, and a slip ringto the negative electrode brush 110.

A light source 113 and a photodetector 114 are disposed on the brushholder 125 so as to face each other on mutually opposite sides of thepositive electrode brush 109. The light source 113 and the photodetector114 are constituted by a light-emitting diode and a phototransistor, forexample, and are disposed facing the brush holder 125 so as tocorrespond to an allowable push-out limit position of the positiveelectrode brush 109.

Thus, in a normal state, the positive electrode brush 109 is between thelight source 113 and the photodetector 114, and the photodetector 114does not receive any light from the light source 113. Then, when thepositive electrode brush 109 is abraded to the abrasion limit, thephotodetector 114 receives light from the light source 113, and anelectric current flows. This electric current is amplified by atransistor 115, and is converted by a Zener diode 118 so as to obtain aconstant voltage. This constant voltage is applied to an astablemultivibrator 112, and the astable multivibrator 112 performslow-frequency oscillation. Because an electric current from a neutralpoint 111 placing a transistor 116 in an ON state by means of a diode119 and a resistor 124 flows into the astable multivibrator 112 througha resistor 123 while the output state of the astable multivibrator 112is at a low level, the transistor 116 is placed in an ON or an OFF statedepending on whether the output state of the astable multivibrator 112is low level or high level. A transistor 117 is switched OFF when thetransistor 116 is ON, and the transistor 117 is switched ON when thetransistor 116 is OFF. In addition, while the transistor 117 is placedin the ON state, an indicating lamp 106 is lit.

In other words, when the positive electrode brush 109 is abraded to theabrasion limit, the astable multivibrator 112 performs low-frequencyoscillation, and the indicating lamp 106 is placed in a periodicflashing state (an abrasion limit sensing indicating state). Thus, bychecking for the periodic flashing of the indicating lamp 106, a vehicleoccupant can recognize that the positive electrode brush 109 has abradedto the abrasion limit and can perform brush replacement. Moreover, ifthe light source 113 and the photodetector 114 are disposed on the brushholder 125 so as to face each other on mutually opposite sides of thenegative electrode brush 110, the abrasion limit of the negativeelectrode brush 110 will be detected. Moreover, power generation isstopped if either the positive electrode brush 109 or the negativeelectrode brush 110 reaches the abrasion limit, and current supply tothe field winding 102 is no longer performed.

However, in conventional automotive alternators, the slip rings rotateduring vehicle operation, and the positive electrode and the negativeelectrode brushes 109 and 110 are constantly and continually beingsubjected to vibration and fluctuation. When roundness of the slip ringsdeteriorates, the vibration and the fluctuation of the positiveelectrode and the negative electrode brushes 109 and 110 increasefurther. There are also influences such as noise, etc., causingdetection output from the photodetector 114 to fluctuate. For thesereasons, one disadvantage has been that malfunctions may arise such asthe abrasion limit sensing indicating state being entered before thebrushes 109 and 110 reach the abrasion limit, or the abrasion limitsensing indicating state not being entered even if the brushes 109 and110 reach the abrasion limit, etc., reducing the reliability of brushabrasion limit sensing.

Furthermore, in conventional automotive alternators, a constant voltagefrom a Zener diode 118 is used as an activating power source for theastable multivibrator 112. However, there are cases in which theelectric current flowing through the photodetector 114 deterioratessignificantly due to the effects of the vibration of the brushes, etc.In other words, the reliability of the supply of current from thephotodetector 114 to the astable multivibrator 112 is low. Because theamplitude of pulse waveforms of this astable multivibrator 112 isdependent on the activating power source, if the electric currentflowing through the photodetector 114 drops, the amplitude of thosepulse waveforms decreases, hindering the operation of the transistors116 and 117 and the lighting of the indicating lamp 106. Thus, anotherdisadvantage has been that even if the brush abrasion limit is sensednormally, there may be insufficient electric power to activate theindicating lamp 106, making it difficult to confirm the periodicflashing of the indicating lamp 106.

In addition, in conventional automotive alternators, because the brushabrasion limit detection and display circuits are constructedindependently from the power generation control apparatus 108, anotherdisadvantage has been that the number of parts and costs are increased.

DISCLOSURE OF INVENTION

The present invention provides an automotive rotary electric machineeliminating malfunctions resulting from vibration and fluctuation ofbrushes and the influence of noise, etc., to increase the reliability ofbrush abrasion limit detection, and eliminating shortages of electricpower for activating indicators to enable stable brush abrasion limitdetection indication to be performed by constructing a determiningcircuit so as to monitor output from a sensing portion for sensing abrush abrasion limit, to detect the brush abrasion limit once thatoutput exceeds a threshold value, and to hold that brush abrasion limitdetection state.

The automotive rotary electric machine according to the presentinvention includes:

a rotor having:

-   -   a field winding for generating a magnetic flux on application of        an excitation current;    -   a plurality of magnetic poles magnetized by the magnetic flux;        and    -   a current receiving portion electrically connected to the field        winding;

a power supply mechanism portion having:

-   -   a brush; and    -   a coil spring for forcing the brush so as to be placed in        contact with the current receiving portion;

a brush abrasion limit sensing portion for sensing that the brush hasabraded to a predetermined length; and

a brush abrasion limit detecting means constructed so as to monitor anoutput from the brush abrasion limit sensing portion, to enter a brushabrasion limit detection state at a point in time when the outputexceeds a set value, and thereafter to maintain the brush abrasion limitdetection state regardless of a magnitude relationship between theoutput and the set value.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal section showing an automotive alternatoraccording to a preferred embodiment of the present invention;

FIG. 2 is a perspective showing a vicinity of brushes in the automotivealternator according to the preferred embodiment of the presentinvention;

FIG. 3 is a circuit diagram explaining an electrical circuit of anautomotive vehicle mounted with the automotive alternator according tothe preferred embodiment of the present invention;

FIG. 4 is a block diagram showing control portions of a power generationcontrol apparatus mounted to the automotive alternator according to thepreferred embodiment of the present invention;

FIG. 5 is a circuit diagram showing a brush abrasion limit detectingcircuit mounted to the automotive alternator according to the preferredembodiment of the present invention;

FIG. 6 is a graph showing a waveform output from a voltage comparatorbefore a brush abrasion limit in the brush abrasion limit detectingcircuit mounted to the automotive alternator according to the preferredembodiment of the present invention;

FIG. 7 is a graph showing switching characteristics before a brushabrasion limit of a transistor for lighting an indicating lamp in theautomotive alternator according to the preferred embodiment of thepresent invention;

FIG. 8 is a graph showing a waveform input at the brush abrasion limitin the brush abrasion limit detecting circuit mounted to the automotivealternator according to the preferred embodiment of the presentinvention;

FIG. 9 is a graph showing a waveform output from the voltage comparatorat the brush abrasion limit in the brush abrasion limit detectingcircuit mounted to the automotive alternator according to the preferredembodiment of the present invention;

FIG. 10 is a graph showing switching characteristics at the brushabrasion limit of the transistor for lighting the indicating lamp in theautomotive alternator according to the preferred embodiment of thepresent invention;

FIG. 11 is a circuit diagram explaining an electrical circuit for anautomotive vehicle mounted with a conventional automotive alternator;and

FIG. 12 is a cross section showing a construction of a power supplymechanism portion in the conventional automotive alternator.

BEST MODE FOR CARRYING OUT THE INVENTION

A preferred embodiment of the present invention will now be explainedwith reference to the drawings.

Preferred Embodiment

FIG. 1 is a longitudinal section showing an automotive alternatoraccording to a preferred embodiment of the present invention, FIG. 2 isa perspective showing a vicinity of brushes in the automotive alternatoraccording to the preferred embodiment of the present invention, FIG. 3is a circuit diagram explaining an electrical circuit of an automotivevehicle mounted with the automotive alternator according to thepreferred embodiment of the present invention, FIG. 4 is a block diagramshowing control portions of a power generation control apparatus mountedto the automotive alternator according to the preferred embodiment ofthe present invention, FIG. 5 is a circuit diagram showing a brushabrasion limit detecting circuit mounted to the automotive alternatoraccording to the preferred embodiment of the present invention, FIG. 6is a graph showing a waveform output from a voltage comparator before abrush abrasion limit in the brush abrasion limit detecting circuitmounted to the automotive alternator according to the preferredembodiment of the present invention, FIG. 7 is a graph showing switchingcharacteristics before a brush abrasion limit of a transistor forlighting an indicating lamp in the automotive alternator according tothe preferred embodiment of the present invention, FIG. 8 is a graphshowing a waveform input at the brush abrasion limit in the brushabrasion limit detecting circuit mounted to the automotive alternatoraccording to the preferred embodiment of the present invention, FIG. 9is a graph showing a waveform output from the voltage comparator at thebrush abrasion limit in the brush abrasion limit detecting circuitmounted to the automotive alternator according to the preferredembodiment of the present invention, and FIG. 10 is a graph showingswitching characteristics at the brush abrasion limit of the transistorfor lighting the indicating lamp in the automotive alternator accordingto the preferred embodiment of the present invention.

An automotive alternator, as shown in FIG. 1, is constructed byrotatably mounting a Lundell-type rotor 7 by means of a shaft 6 inside acase 3 constituted by a front bracket 1 and a rear bracket 2 made ofaluminum and fixing a stator 8 to an inner wall surface of the case 3 soas to cover an outer circumferential side of the rotor 7.

The shaft 6 is rotatably supported in the front bracket 1 and the rearbracket 2. A pulley 4 is fixed to one end of this shaft 6, enablingrotational torque from an engine to be transmitted to the shaft 6 bymeans of a belt (not shown).

A pair of slip rings 9 functioning as electric current receivingportions for supplying an electric current to the rotor 7 are disposedon another end portion of the shaft 6 so as to be separated in an axialdirection and be able to rotate together with the shaft 6.

The rotor 7 is constituted by: a field winding 13 for generating amagnetic flux on passage of an electric current; and first and secondpole cores 20 and 21 disposed so as to cover the field winding 13,magnetic poles being formed in the first and second pole cores 20 and 21by the magnetic flux generated by the field winding 13. The first polecore 20 is made of iron, first claw-shaped magnetic poles 22 having atapered shape being formed at a uniform angular pitch in acircumferential direction on an outer circumferential edge portion ofthe first pole core 20 such that a direction of taper of each of thefirst claw-shaped magnetic poles 22 is aligned in an axial direction.The second pole core 21 is made of iron, second claw-shaped magneticpoles 23 having a tapered shape being formed at a uniform angular pitchin a circumferential direction on an outer circumferential edge portionof the second pole core 21 such that a direction of taper of each of thesecond claw-shaped magnetic poles 23 is aligned in an axial direction.The first and second pole cores 20 and 21 are fixed to the shaft 6facing each other such that the first and second claw-shaped magneticpoles 22 and 23 intermesh with each other. In addition, fans 5 are fixedto end surfaces of the first and second pole cores 20 and 21,respectively. The pair of slip rings 9 are electrically connected inseries through the field winding 13.

The stator 8 is provided with: a cylindrical stator core 15; and athree-phase stator winding 16 installed in the stator core 15.

A rectifier 12 for converting alternating current generated in thestator 8 into a direct current is mounted inside the case 3, therectifier 12 being constructed by connecting four diode pairs inparallel, each diode pair being composed of a positive-side diode d₁ anda negative-side diode d₂ connected in series, as shown in FIG. 3.

A power generation control apparatus 18 for adjusting a magnitude of analternating voltage generated in the stator 8 is fixed to a heat sink17.

A power supply mechanism portion 19 is constructed by housing a pair ofbrushes 10 in a brush holder 24 so as to be forced toward the slip rings9 by coil springs 11, and connecting a lead wire 14 to a head portion ofeach of the brushes 10. A detecting terminal 25 functioning as a brushabrasion limit sensing portion, as shown in FIG. 2, is mounted to thebrush holder 24 so as to electrically contact a coil spring 11 when abrush 10 is abraded to the abrasion limit. Moreover, in FIG. 2, brushes10 having different lengths that is, a brush 10 in an initial state anda brush 10 at the abrasion limit are shown to facilitate explanation,but in normal service conditions, the pair of brushes 10 are abradedequally.

Next, operation of this automotive alternator will be explained based onFIG. 3.

First, a starter (not shown) is activated by inserting a key into a keyswitch 35 and turning the key switch 35, driving an engine.

An electric current is supplied to the field winding 13 from a battery36 through the brushes 10 and the slip rings 9, generating a magneticflux. The first claw-shaped magnetic poles 22 of the first pole core 20are magnetized into North-seeking (N) poles by this magnetic flux, andthe second claw-shaped magnetic poles 23 of the second pole core 21 aremagnetized into South-seeking (S) poles. At the same time, rotationaltorque from the engine is transmitted to the shaft 6 by means of thebelt (not shown) and the pulley 4, rotating the field rotor 7. Thus, arotating magnetic field is imparted to the stator winding 16, generatingan electromotive force in the stator winding 16. Thisalternating-current electromotive force passes through the rectifier 12and is converted into a direct current, the battery 36 is charged, andthe current is supplied to an electrical load 38.

Here, the power generation control apparatus 18, as shown in FIG. 4, isprovided with an integrated circuit 30 including first to fourth controlportions 31 to 34.

The first control portion 31 is a means for sensing a state of no powergeneration, monitoring a phase voltage of the stator winding 16 througha P terminal, and lighting an indicating lamp 37 by switching atransistor 29 ON when the phase voltage is 0 V. Thus, a vehicle occupantcan confirm that the alternator is not generating power, that is, thatthe engine has stopped.

The second control portion 32 is a means for sensing a state ofovervoltage, monitoring an output voltage from the rectifier 12 througha B terminal, deciding whether or not that output voltage exceeds asecond set voltage, and lighting the indicating lamp 37 by switching thetransistor 29 ON when the output voltage exceeds the second set voltage.Thus, the vehicle occupant can check for abnormalities (overvoltages) inthe automotive vehicle being operated.

The third control portion 33 is a brush abrasion limit detecting means,monitoring a voltage of the detecting terminal 25 through a Q terminal,deciding whether or not that voltage exceeds a threshold value, andflashing the indicating lamp 37 by switching the transistor 29 ON andOFF when that voltage exceeds the threshold value. Thus, the vehicleoccupant can check for the abrasion limit of the brushes 10.

The fourth control portion 34 is a controlling means for controlling anoutput voltage from the stator 8 so as to be constant, monitoring theoutput voltage from the rectifier 12 through the B terminal, andcontrolling the passage of electric current to the field winding 13 byswitching a transistor 28 ON when that output voltage is less than afirst set voltage, and by switching the transistor 28 OFF when theoutput voltage is equal to or greater than the first set voltage. Thus,the output voltage from the rectifier 12 is controlled so as to remainconstant.

Next, a brush abrasion limit detecting operation by the third controlportion 33 will be explained with reference to FIGS. 5 to 11.

The third control portion 33, as shown in FIG. 5, is provided with: adetermining circuit 42 for determining the brush abrasion limit based ona voltage from a sensing portion 41; and an oscillating circuit 43 formaking the indicating lamp 37 display so as to flash on and off when thedetermining circuit 42 determines the brush abrasion limit. A voltagecomparator COM1 having a single power source is used for thisdetermining circuit 42. The sensing portion 41 is connected to thedetecting terminal 25 through the Q terminal, and an output portion 44is connected to a base of the transistor 29. Moreover, in FIG. 5, Q1 toQ23 are transistors, r1 to r19, and R4 are resistors, C1 is a capacitor,51 to 58 are constant current sources, and COM1 and COM2 are voltagecomparators.

Before the abrasion limit of the brushes 10, the detecting terminal 25is in a state of non-contact with the coil springs 11. At the abrasionlimit of the brushes 10, the detecting terminal 25 is in a state ofcontact with a coil spring 11. At this time, the voltage of thedetecting terminal 25 as shown in FIG. 8, fluctuates due to effects suchas vibration of the vehicle, deterioration in the roundness of the sliprings 9, etc.

This voltage of the detecting terminal 25 is input into the sensingportion 41 through the Q terminal. When the voltage input into thesensing portion 41 is less than a predetermined voltage value (thethreshold value E₀), a transistor Q1 is switched OFF. Thus, apositive-side input of COM1 (an electric potential at A1) is less than anegative-side input (an electric potential at A2), and COM1 is in an OFFstate. In other words, transistors Q3 and Q5 are switched OFF, andtransistors Q4 and Q6 are switched ON. Then, transistors Q8 and Q7switch ON, and output from COM1 (an electric potential at A3) is LOW, asshown in FIG. 6. Thus, a transistor Q9 is switched OFF, and output fromthe determining circuit 42 (an electric potential at A4) is HIGH. As aresult, a transistor Q19 is switched ON.

When the voltage input into the sensing portion 41 is less than thepredetermined voltage value (the threshold value E₀), the transistor Q1switches ON. Thus, the positive-side input of COM1 (the electricpotential at A1) becomes greater than the negative-side input (theelectric potential at A2), and COM1 switches ON. In other words, thetransistors Q3 and Q5 switch ON, and the transistors Q4 and Q6 areswitched OFF. Then, the transistors Q8 and Q7 are switched OFF, and theoutput from COM1 (the electric potential at A3) is HIGH, as shown inFIG. 9. Thus, the transistor Q9 is switched ON, and the output from thedetermining circuit 42 (the electric potential at A4) is LOW. As aresult, the transistor Q19 is switched OFF. At this time, a transistorQ2 switches on, and the transistors Q3 and Q5 switch ON to maintain theON state of COM1, regardless of whether the transistor Q1 is ON or OFF,that is, regardless of the magnitude of the voltage input into thesensing portion 41. In other words, the brush abrasion limit detectionstate is maintained.

At the same time, in the oscillating circuit 43, when a positive-sideinput of COM2 (an electric potential at B1) is greater than anegative-side input (an electric potential at B2), COM2 switches ON. Inother words, transistors Q11 and Q13 switch OFF, transistors Q12 and Q14switch ON, and output from COM2 (an electric potential at B3) is HIGH.Thus, a transistor Q18 is switched ON. At this time, a transistor Q10 isalso switched ON, and the capacitor C1 is discharged through a resistorR4. The electric potential of the capacitor C1 gradually falls, reducingthe positive-side input of COM2 (the electric potential at B1). Then,when the positive-side input of COM2 (the electric potential at B1)becomes less than the negative-side input (the electric potential atB2), COM2 switches OFF. In other words, the transistors Q11 and Q13switch ON, and the transistors Q12 and Q14 are switched OFF. Then, thetransistors Q15 and Q16 switch ON, and the output from COM2 (theelectric potential at B3) is LOW. At this time, the transistor Q18 isswitched OFF. At the same time, the transistor Q10 is switched OFF, andcharging of the capacitor C1 is started. Then, the electric potential ofthe capacitor C1 rises, and when the positive-side input of COM2 (theelectric potential at B1) becomes greater than the negative-side input(the electric potential at B2), COM2 switches ON.

In this manner, the transistor Q18 switches ON and OFF with a period setby a time constant of the resistor R4 and the capacitor C1.

Thus, when the transistor Q19 is in an OFF state, the transistor Q23 isswitched ON and OFF by the transistor Q18 switching ON and OFF. Thus, ONand OFF signals are output from the output portion 44, the transistor 29switches ON and OFF as shown in FIG. 10, and the indicating lamp 37 isdisplayed so as to flash on and off.

On the other hand, when the transistor Q19 is in an ON state, the OFFstate of the transistor Q23 is maintained even if the transistor Q18switches ON and OFF. Thus, an OFF signal is output from the outputportion 44, the transistor 29 is switched OFF as shown in FIG. 7, andthe indicating lamp 37 is switched off.

The flashing display of this indicating lamp 37 is continued until thepower supply inside the circuit switches OFF, that is, until the keyswitch 35 is switched OFF. For that reason, the flashing display of theindicating lamp 37 is not performed when the key switch 35 is OFF, andthe flashing display of the indicating lamp 37 is resumed if the keyswitch 35 is switched ON again. The vehicle occupant is made aware ofthe abrasion limit of the brushes 10 by visually checking for theflashing display of the indicating lamp 37. Then, the rotation of theengine is stopped by switching the key switch 35 OFF, wiring on thenegative side of the battery 36 is disconnected, and replacement of thebrushes 10 is performed. When the key switch 35 is switched ON afterreplacement of the brushes 10, since the coil springs 11 and thedetecting terminal 25 are in a state of non-contact, the flashingdisplay of the indicating lamp 37 is cancelled.

Thus, in the present invention, a determining circuit 42 is constructedsuch that a voltage comparator COM1 is placed in an ON state when aninput voltage of a sensing portion 41 exceeds a threshold value (E₀),and the ON state of the voltage comparator COM1 is simultaneouslymaintained. In other words, the determining circuit 42 is constructedsuch that once it is determined that the brushes 10 have reached theabrasion limit, the result of that determination is maintained. Thus, atthe abrasion limit of the brushes 10, that is, when the detectingterminal 25 has come into contact with a coil spring 11, even if theelectric potential of the detecting terminal 25 fluctuates due toeffects such as vibration of the vehicle, deterioration of roundness ofthe slip rings 9, etc., there will be no change in the determination ofbrush abrasion limit sensing, improving the reliability of detection.Similarly, resistance to external noise increases, improving thereliability of detection.

In the determining circuit 42, because a voltage comparator COM1 usedswitches ON based on a magnitude relationship between positive-sideinput and negative-side input, resistance to external noise increases,improving the reliability of detection.

Because the transistor 29 for lighting or flashing the indicating lamp37 is operated directly by output from the power generation controlapparatus 18, the circuit for operating the transistor 29 is constructedinside an integrated circuit, enabling a reduction in the number ofparts, thereby providing a cost reduction effect. In addition, becausethe integrated circuit 30 has a flashing mechanism for the indicatinglamp 37, a reduction in the number of parts is similarly enabled,thereby providing a cost reduction effect.

In conventional devices, because input from a brush abrasion limitsensing portion (the light-receiving portion 114) is used as the powersupply voltage for the display circuit (the astable multivibrator 112)for the indicating lamp 106, problems arose, such as the input from thesensing portion fluctuating due to effects such as vibration, etc.,electric power for activating the indicating lamp 106 beinginsufficient, etc., making it difficult to confirm the periodic flashingof the indicating lamp 106. However, in the present invention, becausethe power supply voltage of the signal generating circuit 43 forflashing the indicating lamp 37 is supplied from the battery 36 througha constant voltage circuit, the oscillating operation thereof does notdepend on the input from the brush abrasion limit sensing portion,making it stable, and the above problems do not arise.

Because the third control portion 33 for sensing the brush abrasionlimit is constructed on a single integrated circuit 30 together with thefirst control portion 31 for sensing a state of no power generation inthe alternator, the second control portion 32 for sensing a state ofovervoltage of the alternator, and the fourth control portion 34 forcontrolling the output voltage of the alternator so as to be constant,the number of parts is reduced, enabling costs to be reduced.

Because the construction is such that the brush abrasion limit isannounced by the flashing display of the indicating lamp 37, and thestates of no power generation and overvoltage are announced by a litdisplay of the indicating lamp 37, the vehicle occupant can easilydifferentiate between the brush abrasion limit from the states of nopower generation and overvoltage.

Moreover, in the above embodiment, the determining circuit 42 and theoscillating circuit 43 are constructed so as to operate independently,but similar effects can also be achieved by connecting output from COM1of the determining circuit 42 in series with the oscillating circuit 43.

In the above embodiment, resistance to noise can be increased if acapacitor is inserted between the sensing portion 41 and the base of thetransistor Q1.

In the above embodiment, a function for warning of a brush abrasionlimit (the third control portion 33) is explained as being added to apower generation control apparatus 18 having a power generation controlfunction (the fourth control portion 34) and diagnostic functions (thefirst and second control portions 31 and 32), but it goes without sayingthat a function for warning of a brush abrasion limit may also be addedto a power generation control apparatus having only a power generationcontrol function.

Although not mentioned in the above embodiment, it is desirable for theabrasion limit of the brushes 10 to be announced such that apredetermined remainder remains relative to the abrasion limit. In thismanner, normal operation for a predetermined distance becomes possibleafter the flashing display of the indicating lamp 37 is started,preventing the alternator from entering a state of no power generationbefore replacement of the brushes, etc.

In the above embodiment, the determining circuit 42 determines the brushabrasion limit based on the voltage of the detecting terminal 25, butthe determining circuit 42 may also determine the brush abrasion limitbased on an electric current flowing through the detecting terminal 25.

In the above embodiment, the brush abrasion limit sensing portion isexplained as being constructed so as to sense the abrasion limit of thebrushes 10 by contact between a detecting terminal 25 and a coil spring11, but the brush abrasion limit sensing portion is not limited to thisconstruction and, for example, a construction in which a light sourceand a photodetector are used and the abrasion limit of the brushes 10 issensed by the photodetector receiving light from the light source isalso acceptable.

The above embodiment is explained as it applies to an automotivealternator, but it goes without saying that the present invention is notlimited to alternators, and can be applied to any rotary electricmachine such as an alternating-current motor, an alternating-currentgenerator-motor, etc.

INDUSTRIAL APPLICABILITY

As explained above, because a rotary electric machine according to thepresent invention can achieve sensing of a brush abrasion limit highlyreliably and inexpensively, it is useful as a rotary electric machinefor mounting to an automotive vehicle such as automobile, etc.

1. An automotive rotary electric machine comprising: a rotor having: a field winding for generating a magnetic flux on application of an excitation current; a plurality of magnetic poles magnetized by said magnetic flux; and a current receiving portion electrically connected to said field winding; a power supply mechanism portion having: a brush in contact with said current receiving portion; a brush abrasion limit sensing portion for sensing that said brush has abraded to a predetermined length; a brush abrasion limit detecting means constructed so as to monitor an output from said brush abrasion limit sensing portion, to enter a brush abrasion limit detection state at a point in time when said output exceeds a set value, and including switching means for thereafter maintaining said brush abrasion limit detection state regardless of whether said output exceeds said set value; a stator having a stator winding in which an electromotive force is generated on application of a rotating magnetic field accompanying rotation of said rotor; and a controlling means for controlling an output voltage from said stator so as to be constant, wherein said brush abrasion limit detecting means and said controlling means are constructed in a single integrated circuit.
 2. An automotive rotary electric machine comprising: a stator having a stator winding; a rotor having: a field winding for generating a magnetic flux on application of an excitation current; a plurality of magnetic poles magnetized by said magnetic flux; and a current receiving portion electrically connected to said field winding; a power supply mechanism portion having: a brush in contact with said current receiving portion; a brush abrasion limit sensing portion for sensing that said brush has abraded to a predetermined length; a brush abrasion limit detecting means constructed so as to monitor an output from said brush abrasion limit sensing portion, to enter a brush abrasion limit detection state at a point in time when said output exceeds a set value, and including switching means for thereafter maintaining said brush abrasion limit detection state regardless of whether said output exceeds said set value; means for sensing at least one of a state of no power generation and a state of overvoltage by monitoring an output voltage of said stator, and a controlling means for controlling an output voltage from said stator so as to be constant; wherein said means for sensing at least one of a state of no power generation and a state of overvoltage is constructed in a single integrated circuit; and wherein said brush abrasion limit detecting means and said controlling means are constructed in a single integrated circuit.
 3. An automotive rotary electric machine comprising: a rotor having: a field winding for generating a magnetic flux on application of an excitation current; a plurality of magnetic poles magnetized by said magnetic flux; and a current receiving portion electrically connected to said field winding; a power supply mechanism portion having: a brush in contact with said current receiving portion; a brush abrasion limit sensing portion for sensing that said brush has abraded to a predetermined length; a brush abrasion limit detecting means constructed so as to monitor an output from said brush abrasion limit sensing portion, to enter a brush abrasion limit detection state at a point in time when said output exceeds a set value, and including switching means for thereafter maintaining said brush abrasion limit detection state regardless of whether said output exceeds said set value; means for sensing at least one of a state of no power generation and a state of overvoltage; an indicating lamp; wherein said indicating lamp is constructed so as to flash on and off when said brush abrasion limit detecting means detects a brush abrasion limit, and so as to be continuously lit when said means for sensing at least one of a state of no power generation and a state of overvoltage senses at least one of a state of no power generation and a state of overvoltage. 